1. Field of the Invention
The present invention relates to a formed product of a line-structured substance composed of carbon element, which is so-called carbon nanotube, and a method of forming the same.
2. Description of the Related Art
Many trials have been made on carbon nanotube (CNT), which is a carbon-base, self-organizing, line-structured substance, in applications of various fields, by virtue of its excellent electric, thermal and mechanical properties. Methods for growing CNTs include arc discharge process, laser abrasion process and chemical vapor deposition (CVD) process. There is also provided a technique as disclosed in Patent Document 1, by which CNTs are grown on a cobalt-immobilized simple body such as a titanium-containing zeolite or the like. Among these techniques, the CVD process is widely used in particular in electrical applications because the process can grow CNTs directly on a substrate. Techniques for growing CNTs by the CVD process include such as, as disclosed in Patent Document 2 for example, depositing a catalyst metal film on a substrate by the sputtering process or vacuum evaporation process, refining grains of the film typically by annealing, and allowing CNTs to grow thereon, or in some cases such as depositing a preliminarily-refined particles on a substrate and then allowing CNTs to grow thereon.
In general, as disclosed in Non-Patent Document 1, degree of growth of CNTs by the CVD process is very sensitive to the substrate, so that it is often grown after forming not only the catalyst metal film, but also a metal film composed of aluminum (Al) or titanium (Ti), for example, under the catalyst film. The growth per se is proceeded at a substrate temperature of approximately 500° C. to 1,000° C. while introducing a hydrocarbon gas such as methane, acetylene or the like, or alcohol into a film forming chamber.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-131360    [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-26532    [Non-Patent Document 1] Nihei et al., 2004 Spring Meeting of The Japan Society of Applied Physics and Related Societies, 28p-ZX-11
The conventional techniques represented by those disclosed in Patent Documents 1 and 2, however, are disadvantageous in that the growth of CNTs strongly depends on the substrate on which the catalyst metal film is formed. It is therefore absolutely impossible to grow CNTs directly on a desired substrate typically for the purpose of fabricating electric devices. Applicable ranges of CNTs are therefore strongly limited, and restricted to an extremely narrow range.
The present invention is conceived after considering the above-described problems, and an object thereof resides in providing a formed product of line-structured substance composed of carbon element and a method of forming the same, both of which are aimed at making it possible to readily and reliably form CNTs independent of the substrate allowing the catalyst metal to deposit thereon, or underlying material, even for the case where the substrate is not used.